Silver-coated three-core fiber Michelson interferometer for liquid-level measurement

Abstract

Abstract The Michelson liquid-level sensor based on silver coated the end face of the three-core fiber reflection structure has been proposed to measure continuous or discrete liquid level. The Michelson interference structure can be obtained by the combination of the single-mode optical fiber and the three-core optical fiber with the silver film coated on the other end face of it. The inter-mode interference can be obtained by the fiber-core mismatch at the fusion joint. The liquid level can be measured by monitoring the dip wavelength shift of the interference spectrum. The results indicate that the sensitivity of the liquid-level sensor will decrease with the increasing sensing length. The sensing length of 30 mm is selected to investigate the performance of the sensor. The sensitivity of water level is reached as high as 392.83 pm/mm with an excellent linearity of 0.99946. Interestingly, the sensitivity of the sensor increases with the liquid refractive index and the sensitivity of the refractive index for NaCl solution is 4410.74 pm/mm/RIU. The performance of the sensor is very stable in the range of 20–90 °C. The maximum drift for temperature is 0.3001 nm. The sensor can be applied to the measurement of the liquid level in different environments.